Reiter is set to become the first member of an International Space Station crew who is not from the United States or Russia, dominant partners in the 16- nation program.

The European Space Agency has spent more than $6 billion on its Columbus research space module, which was built to link up with the station.

But its launching, like many other components of the half-built station, has been on hold pending a successful return to flight of NASA's shuttles.

"We are all desperately waiting for the moment when Columbus will be docked to the station," Reiter said.

In addition to design and manufacturing expenses, the European agency pays about $500 million a year for operational costs stemming from the Columbus program, making it the single most expensive space project undertaken by Europe.

"The budgets are set. And due to all these incidents that we had, of course everybody understood that this causes a delay," said Reiter, referring to NASA's problems with the shuttle.

NASA had hoped that its initial redesign, which was tested during Discovery's launching in July 2005 on the first post-Columbia mission, would clear the path to resume station assembly.

But Discovery's tank, like Columbia's, shed large pieces of foam insulation, prompting another wave of modifications.

Throughout the downtime, Reiter kept training. As delays mounted, he shifted from one space station crew to another, eventually ending up with a scheduled 145-day flight that straddles the ongoing Expedition 13 mission and the next increment, which is targeted to begin in September.

A latecomer to the Discovery crew, Reiter nonetheless said he felt at ease with his six shuttle crew mates. The British-born Piers Sellers, who became a U.S. citizen in 1991 and joined NASA's astronaut corps five years later, will also be aboard.

Rounding out the crew are Commander Steve Lindsey; Mark Kelly, the pilot; Lisa Nowak, the flight engineer; Michael Fossum, designated to walk in space; and Stephanie Wilson, the mission specialist.

As far as the risks of flying on the shuttle, Reiter said he was sure it had never been safer.

"Everything has been done to minimize the risk," he said.

Space flight in general requires participants to accept higher risk, he added.

"This is a decision we take at the very beginning," Reiter said. "We are aware that there is a higher risk, and we balance it against what we gain in experience, in knowledge. It's why we do exploration."